| Objective To explore the methodology of observing trachea and bronchus in the fetuses by prenatal ultrasound and to measure relevant parameters, establish their normal reference value range. To lay foundation for diagnosing related diseases, and to explore a new reference for the judgment of fetal visceral position. MethodsNormal group: 1007 normal fetuses from 20 to 39+ 6 weeks of gestation were observed by ultrasound at the coronal section of trachea and bronchus. The subjects were classified into five groups according to gestational age to calculate demonstration rate: group A: 349 cases, 20-23 weeks; group B: 121 cases, 24-27 weeks; group C : 166 cases, 28-31 weeks; group D: 175 cases, 32-35 weeks and group E: 196 cases, 36-39 weeks. The fetuses whose trachea and bronchus were clearly shown were grouped by each gestational week to measure the diameters of trachea and left/right bronchus(DT, DLB, DRB), the angles between them( α, β) and the length of right bronchus(LRB).Patient group: To indentify the clinical value of the research in diagnosing related diseases, 37 cases were studied in the same way as normal group, including 12 cases of visceral abnormal position, 4 cases of trachea bronchial disease and 21 cases of right-sided aortic arc.Statistical approach: Correlation analysis was adoped to find the relationship between those parameters and gestational week. Z-scores analysis was applied in the parameters which were obviously correlated to gestational age. The demonstration rates of each group were compared by chi-square test. Two independent sample t-test was used to analysis the difference between DLB and DRB, α and β. ResultsNormal group: The figure of trachea and bronchus was anechoic and similar to an inverted Y shape at coronal standardized views. The right bronchus was thick, short and steep, while the left was thin, long and smooth relatively. Azygos vein was located in the anterior lateral of the initial segment of right bronchus. There were 602 fetuses whose trachea and bronchus could be demonstrated clearly(59.8%). The numbers and demonstration rates of each group were following: group A 189(54.2%), group B 98(81%), group C 115(69.3%), group D 97(55.4%) and group E 103( 52.3%). The results of both group B and C were significantly higher than others(P< 0. 05). In normal group, DT ranged from 2.03 to 4.40 millimeter, and DLB ranged from 0.87 to 2.07 millimeter, while DRB ranged from 0.97 to 2.37 millimeter.(DRB+DLB)/DT was between 0.91 and 1.13 showing that(DRB+DLB)was approximate to DT. DT, DLB and DRB were significantly positive correlated to gestational age(r = 0. 869, 0.663 and 0. 647 respectively, P< 0. 0001). LRB was positive correlated to gestational age(r = 0. 402, P< 0. 0001). Both α and β had no correlation with gestational age( P>0. 05). α was smaller than β(P< 0. 05). DRB was larger than DLB in some gestational weeks(p<0.05,22-24 w, 27 w, 31 w, 36 w, 39w). The frequency distribution graphs of the Z-scores of DT, DLB and DRB were normal distribution. 95% of the Z-scores of DT, DLB and DRB were between negative two and two in their scatter chars.Patient group: 12 cases of abnormal visceral position were collected including seven situs inversus and five right isomerism. There were six cases of situs inversus whose ultrasonic image showed that α was bigger than β, while one case of situs inversus partialis showed the opposite. Among the cases of right isomerism, four displayed that α was similar to β, and one was tracheal bronchus. Four right isomerism and one situs inversus were confirmed by autopsy. There were four cases of trachea-bronchial diseases which were all confirmed by autopsy. Among the four cases, one case of congenital high airway obstruction revealed that trachea dilated obviously, and two cases of tracheal bronchus showed that a right upper bronchus originating in the trachea. One case of tracheal bronchus was missed in prenatal ultrasonography, while the autopsy showed that both right and left upper bronchus originating in the trachea. There were 21 cases of right-sided aortic showing that trachea lay on the right of the aortic. The trachea was compressed in 20 cases to different extent. One case of right-sided aortic arc was confirmed by autospy. One case of right-sided aortic arc was gurgling with sputum during neonatal period, while another showed hoarseness in infancy period. O ne case was preterm. Seven cases were in good condition after birth, while 5 cases were lost to follow-up. ConclusionsIt is feasible to observe fetal trachea and bronchus at the coronal view of thorax. The appropriate gestational age for ultrasonic observation is 24-31+ 6 weeks. The diameter of trachea and bronchus and the angle between them can be potential valuable for assessing the growth of trachea and bronchus prenatally. It may also provide a new horizon for judging visceral position and diagnosing related diseases. |
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